DE746320C - Device to protect the tube flow meter in an X-ray system - Google Patents

Description

Device for protecting the tube ammeter in an X-ray system It is well known that in X-ray systems there are very varied values of the tube amperage worked. During recordings, a current of several hundred milliamps a few milli.anipers are sufficient for fluoroscopy to flow through the tubes. In In view of the great diversity of the current intensities, the tube ammeter is used equipped in a known manner with several measuring ranges, and for example is during the transition from exposure to transillumination = do-, which usually takes place very quickly, at the same time the smaller measuring range of the tube ammeter is switched on. As a result the thermal inertia of the hot cathode of the X-ray tube decreases during the transition Tube current strength not instantly on the fluoroscopic value, but - required to do this a certain short time. In this short time, however, the tube ammeter, whose smaller measuring range is already switched on. is to be overloaded.

According to the invention, the tube ammeter when transitioning to a smaller current range and simultaneous instantaneous transition to a smaller one The measuring range is protected from overload by a resistance in Series is connected to the ammeter and that a parallel to this arrangement Discharge path, in particular a glow lamp, is switched, whose response when a current that exceeds the measuring range of the ammeter occurs causes the overvoltage occurring at the corresponding biemes, enen resistor will. The response of the discharge path causes the tube current to be too strong past the ammeter. As soon as the current has dropped sufficiently, the discharge line goes out, and the current just flows again via the tube ammeter.

It is well known in many X-ray facilities. a glow lamp assembly used to rectify the alternating current for the tube ammeter. In such a case, the glow lamp arrangement can itself be used as a discharge path to be used. The relatively high voltage drop that occurs across the series the ammeter connected resistance occurs, namely that the glow lamps `` lose their rectifying effect and thereby keep a watchful eye for so long to form the tube ammeter until the tube amperage and thus the voltage drop at which the resistance has decreased sufficiently.

To protect the tube ammeter against high frequency interference, it is expedient to run parallel to the discharge path and thus also to the series circuit arrangement of tube ammeter and resistor to switch a capacitor.

Embodiments of the invention are shown in Figs. I and 2 of the circuit arrangement shown schematically after.

In the embodiment according to Fig. I, the X-ray tube i is fed by the high-voltage transformer 2, the secondary winding of which consists of two identical parts 3 and 3 ″, the connection point of which, ie the electrical center point of the high-voltage transformer, is grounded. The primary winding .1 of the high-voltage transformer 2. All the mains is connected. The tube current is switched on between the two secondary windings 3 and a of the high-voltage transformer 2. When the switch 7 is in the position,>, the large measuring range of the tubular stroniniesser 6 is switched on. At the transition from exposure to fluoroscopy, the small measuring range of the ammeter 6 is switched on, and at the same time the switch 7 is placed in position g, so that the resistor io is connected in series with the ammeter 6. The voltage drop that occurs in all this resistance brings the discharge path ii to respond briefly, whereby the Ammeter 6 is protected from overload. Parallel to. the discharge path ii; the capacitor 12 is located.

In the embodiment according to FIG. 2, that of the X-ray tube i current supplied via the high-voltage valve tubes 13, 1.4, i 3 and 16 in a Graetz circuit rectified. The tubular ammeter 6 is also corresponding in a known manner connected to a glow lamp arrangement serving for rectification, which consists of the glow lamps 17, iS, i9 and 20 connected together in Grätzschaltang. As a result of the high voltage drop across the resistor io, the glow lamps 17 lose and i9 or i S and 2o their rectifying effect, so that the tube current of 21 via Lanipeu 17 and 18 or. 19 and 20 immediately after 22, i.e. on the tube ammeter 0, bypass it.

Claims (2)

PATENT CLAIMS: i. Device to protect the tubular ammeters in an X-ray system from overload when transitioning to a smaller current range and at the same time instantaneous transition to a smaller measuring range, characterized in that (during the transition, a resistor is connected in series with the ammeter and (iaß parallel to this arrangement zero) a discharge path, in particular a glow lamp, is connected, the general speaking of which is caused by the overvoltage occurring at the correspondingly dimensioned resistor when a current occurs which exceeds the measuring range of the ammeter. 2. Device according to claim i, characterized in that a glow lamp arrangement is used as the discharge path is, which in all known manner to rectify the alternating current for the tube ammeter is used. ;. Device according to claim 1 or 2, characterized in that that a capacitor is connected in parallel with the discharge path.